Manufacture of depolarizers for galvanic cells



Patented Jan; 12, was

NIKOLAI AHLMANN, OF COPENHAGEN, DENMARK, AS SIGNOR TO F. L. S MIDTH & 00., OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY MANUFACTURE OF DEPOLARIZERS FOR GALVANIC CELLS No Drawing. Application filed October 30, 1930, Serial No. 492,375, and in Denmark December 4, 1929.

In the manufacture of galvanic cells with a depolarization paste consisting of a mixture of manganese dioxide and graphite, the constituents must be as intimately mixed as possible. The mixture has been made by grinding the constituents separately to a suitable size of grains and then mixing them thoroughly in the proportion which in practice has proved the mostadvantageous, but it has also been tried to solve the problem by grinding the constituents together in a suitable grinder, whereby it has been sought to obtain partly a grindingof the constituents to about the same size of grains, partly an intimate mixing of the ingredients.

It has now appeared, in the development of the present invention, that a considerably improved efiiciency of the manufactured product is attained when the grain size of the graphite materially exceeds the grain size of the manganese dioxide. In such case the mixture must, however, as heretofore, be as homogeneous as possible.'

The object of this invention is to render possible the realization of this discovery by a special method for producing the paste. The characteristic of this method is that the two materials are ground simultaneously and subjected to air sifting in a known manner such as that used, for instance, in certain cases for grinding of cement, or to an air separation of a similar nature. The purpose is that the graphite grains of the mixture shall be essentially larger than the manganese dioxide grains, and this result is easily accomplished by air sifting because the specific gravity of the manganese dioxide is higher than that of the graphite, so that the graphite grains carried by the current of air applied will be larger than the manganese dioxide grains. The proportions between the sizes will be such that the weights of the grains are practically alike for the two constituents.

This method can be practiced either in grinding in a mill embodying an air sifting device, or in grinding in an ordinary mill With subsequent air sifting in a machine specially designed for that purpose.

The ingredients can be weighed oil in exactly correct quantities before the grinding, or the composition of the mixture resulting from the grinding and sifting can be corrected by admixing of either ingredient of a suitable grain size.

I claim as my invention:

1. The process of manufacturing depolarizationpaste from graphite and manganese dioxide for galvanic cells, in which the ingredients, in correct or approximately correct proportional quantities, are ground together and are subjected to air sifting so that the grain size of the graphite in the finished mixture will exceed that of the manganese dioxide.

2. The process as set forth in claim 1 and in which a quantity of one ingredient of a suitable, grain size is added after the grinding to correct the composition of the mixture.

This specification signed this 17 day of October, A. D. 1930.

NIKOLAI AHLMANN. 

